This week I have received two dinner invitations via Twitter direct message; they bounced into my iPhone as email alerts. I was asked if I would like to write this piece via an email, which announced itself with a ping while I was walking along the Cornish coastal path, and to which I replied with a terse "OK". I can't remember the last time I actually spoke to the person who'd commissioned it, for talking to people for work-related purposes has become the communication of last resort, only necessary when you have complex problems that require direct speech to iron out.

In an era when literacy and the written word are supposed to be in decline, much of what we say to each other relies on typing on various kinds of screen, in the home and outside it. Ofcom has just announced that there has been a 5% fall in calls made on landlines and mobiles. In 2011, 58% of people sent texts, while only 47% used their mobiles to speak to someone. Now that 39% of the population owns smartphones, the written word – in the form of emails, texts and Google searches – has overtaken the ringtone. Making calls and speaking to someone has become the heritage technology on phones, a quaint reminder of the days when they were black plastic bricks with antennae carried by advertising executives shouting that they were on the train. On Monday the novelist Jon McGregor created an ongoing Twitter short story about a mysterious train journey to Matlock while on the train, and I read it, in the quiet carriage with the ringer off, on another train on a different journey.

The uses of the smartphone are endless but the number of calls made on them is declining, while landlines gather dust, rung only by cold callers selling double glazing. Interrupting someone's day to ring them always seemed to me an intrusion when you had no idea what they might be doing when you rang ("I'm in the queue to board a plane. Is this urgent?"), and voicemail messages sound incoherent compared with the tersely eloquent text message, which gets straight to the point. Twitter and Facebook messages come directly into my email inbox. Until I disabled them, I was assaulted with alerts and badges telling me someone had made contact.

When I got an email account in the late 90s, I encouraged people to use it, rather than ring me so I could work in peace, uninterrupted. I still prefer to email so that the recipient has a record of what it is I'm contacting them about and I can refer them back to it if there is confusion. Gradually, my phone ceased to ring. I discouraged people from calling my mobile unless it was urgent, as I reasoned that, if I was out, I was out, and talking to my editor about proofs while about to get on a bus seemed pointless.

Now both my phones have fallen silent. I use the landline to ring various customer service departments, but even my GP's surgery offers the opportunity to make an appointment online. The telephone chat, the enjoyable 40 minutes chewing over the gossip, seems to be passing into history. I seem to use the phone more to text to co-ordinate my face-to-face meetings than to speak to anyone. The rushed, expensive international call, the meter clocking up the charges, has been replaced by Skype.

Perhaps in the future the idea of talking to a disembodied voice will seem as bizarre as it did to Proust when, in Remembrance of Things Past, he describes the narrator's first ever phone call, to his grandmother. Yet I miss the intimacy of this most direct of speech, the voice in your ear talking straight into your own head. You missed the body language but, without it, the inflection of the voice was magnified. I felt I could really concentrate when I had a phone conversation, until I noticed the suspicious clicking at the other end of the line of the fingers playing computer solitaire or even answering emails. Perhaps all that will be left in the end is phone sex, as porn, like cockroaches, inherits the earth.